Field
Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to a method and apparatus for improving downlink performance in a wireless network.
Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems and Orthogonal Frequency Division Multiple Access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-input single-output, multiple-input single-output or a multiple-input multiple-output (MIMO) system.
Transceivers with multiple antennas may implement any of various suitable diversity schemes in an effort to increase the reliability of transmitted messages through the use of two or more communication channels with different characteristics. Because individual channels may experience different levels of interference and fading, such diversity schemes may reduce the effects of co-channel interference and fading, as well as avoid error bursts.
One type of diversity scheme utilizes space diversity, where a signal may traverse different propagation paths. In the case of wireless transmission, space diversity may be achieved through antenna diversity using multiple transmitting antennas (transmit diversity) and/or multiple receiving antennas (receive diversity). By using two or more antennas, multipath signal distortion may be eliminated, or at least reduced. In the case of receive diversity with two antennas, the signal from the antenna with the least noise (e.g., highest signal-to-noise ratio (SNR)) is typically selected, while the signal from the other antenna is ignored. Some other techniques use the signals from both antennas, combining these signals for enhanced receive diversity.